Accession Number : ADA311635

Title :   Materials for Adaptive Structural Acoustic Control. Volume 1.

Descriptive Note : Annual rept. 1 Feb 95-31 Jan 96,

Corporate Author : PENNSYLVANIA STATE UNIV UNIVERSITY PARK MATERIALS RESEARCH LAB

Personal Author(s) : Cross, L. E.

PDF Url : ADA311635

Report Date : 13 MAR 1996

Pagination or Media Count : 200

Abstract : This report documents work carried forward over the fourth year of a five year ONR sponsored University Research Initiative (URI) entitled 'Materials for Adaptive Structural Acoustic Control.' The program has continued to underpin the development of new electroceramic, single crystal and composite materials combinations for both the sensing and actuation functions in adaptive structures. For the lead based perovskite structure relaxor ferroelectric electrostrictors, new experimental and theoretical studies have underscored the critical role of nano-scale heterogeneity on either A or B sites of the ABO3 in promoting dispersive dielectric response and the very strong opposing role of elastic stress and electrostrictive coupling in suppressing polarization fluctuations. Most important for practical application is the regimen where, under high electric field nano-polar regions begin to amalgamate into ferroelectric macro-domains with very mobile walls lead to unusually large extrinsic piezoelectric coefficients. The program has explored a range of new relaxor-ferroelectric solid solutions which exhibit morphotropic phase boundaries between rhombohedral and tetragonal ferroelectric phases. Some of these compositions are much more tractable than PZT to grow in single crystal form. A major surprise is the very strong enhancement of the piezoelectric d sub 33 and d sub 31 in the crystal over that in the corresponding ceramic, and the massive anisotropy for different orientations and directions of poling. Optical studies suggest that the unusual effects reside largely in the extrinsic (domain controlled) response and we speculate about the mobility of walls in metastable phases, however further studies are required.

Descriptors :   *ADAPTIVE CONTROL SYSTEMS, *STRUCTURAL PROPERTIES, *COMPOSITE MATERIALS, *PIEZOELECTRIC MATERIALS, *ACOUSTICS, *FERROELECTRIC MATERIALS, STRESSES, COUPLING(INTERACTION), OPTICS, POLARIZATION, MOBILITY, EXPERIMENTAL DATA, ELASTIC PROPERTIES, THIN FILMS, DIELECTRICS, SINGLE CRYSTALS, PHASE, VARIATIONS, CERAMIC MATERIALS, ANISOTROPY, PIEZOELECTRICITY, WALLS, LEAD COMPOUNDS, TITANATES, LANTHANUM, ELECTROSTRICTION, ACTUATION, METASTABLE STATE, ZIRCONATES, DISPERSIONS, PEROVSKITES, STANNATES.

Subject Categories : Laminates and Composite Materials
      Inorganic Chemistry
      Ceramics, Refractories and Glass
      Acoustics
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE